ridge vent w/ roof louvres?

Well, I guess I have 2 different answers. Perhaps more background info will help. The west side (front) has 2 gables w/o ridge vents, only a couple of soffit vents on the sides and near the peak. The covered porch has no soffit vents (plan on installing continuous vent since we've had problems w/ ice dams) and is steep (about 12/12 I think).

The back side w/ the louvres is shallower (don't know exact pitch, maybe 3/12) and has some soffit vents (1 about every 5 or 6 ft).

How can I evaluate the ventilation to see if I need more or less exhaust or intake?